Vert Phys Study Guide exam1

Vert Phys Study Guide exam1 - Vert Phys Study Guide Exam#1...

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Vert Phys Study Guide: Exam #1 Introduction to the Nervous System Cells comprising intracellular organisms are highly interdependent – intercellular communication Endocrine system Communication accomplished by hormone diffused or carried by circulation between cells Slow Number of unique signals that can be sent is limited by number of hormones Nervous system Communication by electrical signals conducted between specialized cells Rapid One signal can be used to mean many different things depending upon the particular neural circuit in which it is occurring Can be divided into two different systems: Central: Consists of that portion of the nervous system enclosed within the bony structures of the skull and vertebrae Most of the neurons here are interneurons Both innervated by and innervates only other neurons Peripheral: Consists of nerves running to and from these central structures Axons which run in the peripheral nerves are often classified as either afferents or efferents Efferent: convey nerve impulses away from CNS EX: Motor neuron
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Afferent: convey nerve impulses towards the CNS EX: Sensory axon Stretch Reflex: “Knee Jerk” Relfex Two types of neurons involved: Sensory and motor Sensory: consists of a long axon which runs in a peripheral nerve to the spinal cord Hammer tap stretches tendon, which, in turn, stretches sensory receptors in leg extensor muscle EM: When active, contracts causing leg to extend Tendon attached to bone, runs over knee and is what is struck with hammer Striking tendon pulls on the muscle and stretches it slightly Sensory neuron synapses with and excites motor neuron in the spinal cord Axon goes into spinal cord and another runs in opposite direction to the muscle spindle (sensory receptors) Axon directed toward the spinal cord enters the spinal cord where it branches and makes synapses with the dendrites of neurons located in spinal cord (spinal motor neuron) Stretching of a muscle produces a receptor potential in terminal fibers of sensory neuron Sensory neuron also excites spinal interneuron which synapse inhibits motor neuron to flexor muscles Stretch causes the generation of an electrical signal in the sensory axon ending which is measured as a potential change: local potential/receptor potential If receptor potential is sufficiently large, it will initiate a second type of electrical signal at or near the afferent axon endings on the muscles spindle: action potential Motor neuron conducts AP to synapses on EM fibers causing contraction
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FM relaxes because activity of its motor neuron has be inhibited In order for AP to be initiated, LP must be at least of a certain critical amplitude or threshold AP propagates along axon and continues to be conducted until it reaches the synapses made by the axon endings and abruptly ceases Synaptic potential: When chemical transmitter substance released by AP reaches membrane of motor neuron, combines with receptor molecule Causes a local potential change in dendrite of motor neuron Leg extends
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